A malamine resin has been conventionally and widely employed as a molding compound, a facing material, a curing agent for coatings, and an adhesive for woody materials, etc. because of excellent heat resistance, high hardness, high gloss, quick curability, and an excellent mold release property in molding.
On the other hand, melamine is hexa-functional, and a triazine skelton is rigid. Accordingly, a crosslinking density in a cured product therefrom becomes exceedingly high in a case of preparing a resin with formaldehyde, whereby it is very hard and excellent in heat resistance. Contrarily, however, it is brittle, and there has been limitation in a case that the molding compound is employed as industrial parts.
For that reason, in a case that it is employed as molding compound, it has been attempted that the melamine resin has been modified by a rubber or phenol. However, a sufficient effect has not been obtained in the existing circumstances. Further, although the addition of various kinds of alcohols and saccharides into a melamine resin composition has been attempted for improving crack resistance and mechanical strength. However, in a case that co-condensation has not been sufficient in the preparation, there has been drawbacks to cause a decline of mechanical strength, a decline of crack resistance, and a decline of glossiness in surface because additives cause bleedout with a lapse of time.
Still further, the melamine resin in mainly employed in a baking coating as a curing agent for an alkyd resin, and it is excellent in heat resistance, light resitance, and resistance to scratching. On the other hand, it is poor in bending ability of a coating layer and post processability. For that reason, guanamines such as benzoguanamine and acetoguanamine are occasionally employed. However, benzoguanamine resin has benzene group in the structure and accordingly, it has been known that it in poor in light resistance and thus, it is limited in utilization. Also, a melamine-formaldehyde resin is poor in solubility in organic solvents and, for that reason, in the case that it is employed as an organic solvent-based coating, a melamine-formaldehyde reaction product has been dissolved into solvents by further alkoxylation with alcohols such as methanol, ethanol, propanol, isopropanol, and butanol. However, alkoxylation reaction has drawbacks that it requires a long time in reaction steps and that as the alkoxylation reaction in conducted in acidic condition, condensation is accelerated and thus, it becomes difficult in controlling a molecular weight.
The melamine resin has been conventionally and mainly employed as a facing material for a horizontal decorated surface in a furniture due to a high hardness, a high heat resistance, and high gloss. In recent years, so-called post-forming processing is frequently put into practice, in which a decorative laminated sheet is post-processed after curing in order to promote features as a design.
Whereas a decorative melamine laminated sheet has a high hardness, cracks are occasionally caused with a lapse of time. Therefore, the improvements in that point have been tried.
For the purpose, it has been conducted an improvement for modifying a melamine resin using various kinds of compounds having copolycondensation, or adding various kinds of additives to the melamine resin so as to improve the post-forming processing property and for crack resistance. however, when an incorporation of the compounds or additives into the resin is poor, water resistance and gloss are lowered. Thus, it can not be necessarily said that sufficient results have been obtained.
Melamine has been frequently employed as adhesives for woody materials in combination with urea. Although it is excellent in processability due to a quick curing rate compared to a phenolic resin adhesive employed in the same kinds of uses, it is disadvantageous to be used to resinous needle-leaf trees which have been often employed in recent years since a melamine resin adhesive itself is poor in a lipophilic nature.
The prevent invention provides an amino resin composition having toughness, bending processability, and a lipophilic nature without a loss of properties such as heat resistance, high hardness, and excellent gloss in the melamine resin.